Over-center, float-operated valve actuating mechanisms have evolved in the past few years, which are highly useful in controlling the filling or near filling of a closed or sealed pressure vessel, which vessel includes a vent valve for venting the interior of the vessel to the atmosphere, and a second pressure gas inlet valve subjected to a high pressure inlet gas, such as live steam at 100 to 500 psi to drive an accumulated liquid periodically from the vessel. One such mechanism is the subject matter of U.S. Reissue Patent RE-34,957 entitled "LEAK PROOF, PRELOADED, HIGH-BIASING FORCE FLOAT-OPERATED OVER-CENTER VALVE ACTUATING MECHANISM" to this applicant and reissued May 30, 1995. The content of this Reissue Patent RE-34,957 is incorporated herein by specific reference.
The over-center valve actuating mechanism of the '957 patent is characterized by a relatively short axial length, large coil turn diameter, stiff compression coil spring having a large spring constant and being subject to spring preloading. Such is not subject to distortion under high preload and the load forces incurred during opening and closing of the valves. The compression coil spring of relatively large coil turn diameter and short length functions adequately as one of the two over-center links while exerting a high biasing force on the over-center valve actuating mechanism.
The over-center toggle linkage valve actuating mechanisms to which the present invention has application is not limited to a toggle linkage mechanism in which a compression coil spring is employed, indeed the invention has application to applicant's U.S. Pat. No. 5,426,990 entitled "OVER-CENTER TOGGLE LINKAGE VALVE ACTUATING MECHANISM WITH ADJUSTABLE TENSION SPRING PRELOADING", issued Jun. 27, 1995 and which is characterized by a toggle linkage mechanism comprised of two solid links, one is of adjustable length relative to the other for preloading one or more tension springs tending to bias the toggle linkage in alternate, cross-over center positions, with the bias maintained continuously throughout the toggle linkage movement to alternate oppositely oblique over-center positions. Further, both of these patents to the applicant are directed to valve actuating mechanisms in which there is no movement of the valve actuator until the two toggle links move into exact alignment at the over-center position, and wherein instantaneously the pressure gas inlet valve and the gas outlet or gas vent valve instantly, alternately open and close.
While the float-operated over-center valve actuating mechanisms of applicant's patents discussed above constitute major improvements within the liquid pump field, such pumps as devised are limited in terms of capacity and internal pressure capability. Attempts have been made to create larger pumps for increased capacity, requiring increased internal pressure for effective operation. The results to date have been disappointing. The simple expedient of increasing the number of gas inlet valves and vent valves allows pump operation, but capacity is still limited.
The applicant is aware of one attempt to manufacture and sell a large condensate pump using direct valve on-off operation. In a first attempt using two valves, a single pressure inlet valve and a single vent valve failed. It is believed that the single valves were simply too large or poorly designed.
In a second known attempt at the creation of a large capacity pump of this nature, a pilot signal from a small valve inside the pressure valve is employed to open an external pilot valve operated by a large valve, which in turn sends pressure into the vessel to pump out whatever liquid or condensate accumulates therein. This leads to a delay between the time the small valve inside the tank opens by its trip point, and pressure is sent through piping back outside the tank to a pilot operated valve. With the pilot pressure being satisfied, the pilot valve opens and operation is effected. Such operation is neither instant nor precise.
It is, therefore, a primary object of the present invention to provide an improved snap-acting, over-center valve actuating mechanism for large capacity liquid pumps having high internal pressure within the pump vessel, which is useful both with compression coil biasing springs and tension springs, which preferably employs a plurality of relatively short axial length, stiff compression coil springs having large spring constant and being of relatively large coil spring diameter, in which the mechanism includes a plurality of balanced coil springs in which the opened and closed gas pressure and vent valves remain in their current state until the over-center toggle linkage moves into alignment and crosses over center, and in which a single vent valve takes the form of a poppet valve assembly having a plurality of circumferentially spaced stand-off rods making three-point contact with the periphery of the poppet valve plug for guiding the poppet valve during the full stroke movement upon valve opening and closing with ensured full seating of the poppet valve plug onto a conical valve seat.